Graft prostheses are often implanted within blood vessels, particularly the aorta or other arteries, which may be subject to aneurysm formation and/or severe atherosclerotic disease which may involve multiple stenoses. For example, an aortic aneurysm may develop in a patient, for example, within the abdominal aorta at the aorto-iliac bifurcation, requiring treatment before the vessel wall ruptures. To repair a blood vessel damaged by such an affliction, a procedure involving use of a graft prosthesis is generally performed.
A number of graft prostheses have been suggested that include a tubular graft attached to a stent. The tubular graft may be a biocompatible porous or nonporous tubular structure to which a stent structure, such as a wire mesh, may be attached. The stent structure may be biased to assume an enlarged configuration corresponding to a target treatment site, but may be constrained in a contracted condition to facilitate introduction into a patient's vasculature. The graft prosthesis may be percutaneously introduced in the contracted condition, advanced to a treatment site within a blood vessel, and released to assume the enlarged condition and repair and/or bypass the treatment site.
One problem often associated with such prostheses is effectively securing the tubular graft at the treatment site. The released graft prosthesis may not sufficiently engage the vessel wall adjacent the treatment site, possibly resulting in the graft prosthesis moving after implantation, which may expose the damaged vessel wall. Plastically deformable expandable stent structures may be provided to attempt to more directly control the engagement between the graft prosthesis and the vessel wall. Such plastically deformable structures, however, may not provide desired flexibility transverse to the longitudinal axis of the stent, making direction through and/or implantation within tortuous body passages difficult. Further, they also generally require the use of a balloon or other expandable member to expand the stent structure to the enlarged condition, which may introduce risks of uneven stent structure expansion and/or balloon rupture.
In addition to plastically deformable stents, coiled-sheet stent structures have been suggested. Coiled-sheet stents may provide enhanced anchoring within the blood vessel because the size of the fully expanded stent may be more precisely controlled. Coiled sheet stents may be substantially evenly expanded and generally do not involve plastic deformation of the stent material. A coiled-sheet stent, however, may be substantially rigid transverse to its longitudinal axis, potentially resulting in a less flexible graft prosthesis, which may not be implanted effectively in tortuous anatomical conditions.
Graft prostheses may also be vulnerable when subjected to longitudinal compression, which is often encountered after implantation. The vessel wall may at least partially recover after a graft has been implanted and the underlying vessel wall no longer experiences substantial blood pressure. If the vessel wall shortens longitudinally during recovery, it may cause the graft material to buckle and kink, thereby potentially constricting flow through the graft prosthesis.
Therefore, there is a need for an improved stent-graft that may provide improved flexibility and/or graft support, while still providing substantial anchoring within a blood vessel.